1. Field of the Invention
The present invention relates to a new and improved multi-stage air bag inflator which is controlled to generate lower or higher level gas flow dependent on the severity of impact. More particularly, the multi-stage air bag inflator of the present invention has a unitary housing divided by an internal wall into at least two separate chambers with each chamber containing a charge of gas generant material and an ignition system therefor. The internal wall is provided with a frangible wall section which ruptures in response to gas pressure in one chamber but is supported against rupture in response to gas pressure in the other chamber. Thus, in response to one level of impact a single chamber is activated and in response to another level, both chambers are activated.
2. Background of the Prior Art
U.S. Pat. No. 5,330,226, discloses a method and apparatus for detecting an out-of-position occupant for controlling the actuation of a vehicle occupant restraint system having a remote vent valve for venting gas generated by one or both inflators provided for inflating a single air bag restraint.
U.S. Pat. No. 5,074,583, discloses an air bag system for an automobile having a housing for containing a plurality of individually controlled inflators, each having a discharge valve designed to open for inflation of an air bag when a gas pressure of more than a predetermined value is generated.
U.S. Pat. No. 5,232,243 discloses an occupant sensing apparatus for use in an occupant restraint system. The disclosed occupant sensing apparatus preferably monitors the passenger seat in the vehicle to detect the presence on an object in the seat, the position of the object and the weight of the object. A control algorithm is performed to control air bag inflation responsive to the detected values.
U.S. Pat. No. 4,243,248 discloses an air bag system including air bags for the driver and a front seat passenger. In the disclosed air bag system, the passenger side air bag can be inflated in two stages in response to an output signal generated from a sensor system when deceleration reaches first and second thresholds.
U.S. Pat. No. 3,767,228 discloses apparatus for controlling the operation of air bag inflation dependent on ambient temperature within the vehicle in which the apparatus is disposed.
U.S. Pat. No. 5,074,583 discloses an air bag system for an automobile including a seating condition sensor that detects a seating condition of a passenger with respect to seat position, reclining angle, passenger size and posture. The air bag is operated in accordance with the seating condition of the passenger so that the inflated air bag is brought into optimal contact with the occupant.
U.S. Pat. No. 4,984,651 discloses a passenger restraint system for motor vehicles including a switch member that detects the functional position of the safety belt. Activation of an air bag and a belt tensioner is dependent on the functional position of the safety belt.
U.S. Pat. No. 4,998,751 discloses a two stage automotive gas bag inflator using igniter material to delay second stage ignition having two compartments with igniter material in a second compartment which burns slower than that in the first compartment.
U.S. Pat. No. 5,071,160 discloses a sensor for detecting the position of the passenger to effect deployment of the air bag to provide optimum protection for the passenger.
U.S. Pat. No. 3,672,699 discloses an automatic restraint system arming control of an air bag dependent on the presence of an occupant to effect inflation of the air bag. If no occupant is present, the air bag is not inflated.
U.S. Pat. No. 4,620,721 discloses an air bag system that also is responsive to the driver's use of a seat belt. The difference is that the threshold speed differs depending on the driver's use of the belt.
U.S. Pat. No. 3,767,002 discloses a seat occupancy responsive air cushion actuation and monitoring circuit that determines passenger occupancy before firing a squib which controls inflation of the air bag.
U.S. Pat. No. 3,966,224 discloses a multiple inflation rate air bag system using an air-augmented inflator which is activated in various manners in accordance with the occurrence of predetermined levels of intensity of impact to provide the multiple rates of inflation.